EP0176963B1 - Process and apparatus for the separation of a complexly composed load from liquid wastes such as industrial waste waters and sanitary landfill leachates - Google Patents

Abstract

The process entails distillation, in particular, for removal of polyhalogenated aromatic and other cyclic compounds, such as HCH, PCB, PCDF, PCDD, in which the waste water, after adjustment of the pH to an acidic or alkaline range, is fractionated in at least one vaporiser stage into vapours and a distillation residue so that at least a part of the volatile load is removed by distillation with the vapours, and the distillation residue is supersaturated in at least one of the constituents; the vapours are condensed and after-treated in a condenser and/or in subsequent vaporiser stages, and the supersaturated distillation residue is drawn off at least in part from the vaporiser stage and subjected to a separation-out of solids, and the clear liquid from which solids have been removed is returned to the vaporiser stage. <IMAGE>

Description

The invention relates to a method and a device for carrying it out which is particularly suitable for cleaning complex-composed, organically and / or inorganically contaminated liquid wastes, in particular industrial wastewater and landfill leachate contaminated in this way, by single- or multi-stage distillative treatment in the acidic or alkaline range with subsequent Aftertreatment of the distillation secondary products.

In particular, the invention also relates to the treatment of the highly contaminated problematic wastes and waste water, which contain polychlorinated organic aromatic and other cyclic organic compounds, and their removal under ecologically and health-relevant acceptable conditions, which has hitherto led to considerable difficulties. This problem has received a lot of public attention with terms like "dioxin", "lindane".

Liquid waste that arises from industrial, municipal and household waste disposal, but especially liquid hazardous waste, contains very different loads of organic and / or inorganic loads, some of which are difficult or not at all biodegradable and cannot be rendered harmless or removed in any other way. Such heavy loads include phenols, naphthenic compounds, mineral oil components and complexing agents as well as other ingredients. The problem is even more serious with landfill leachate, especially from special waste landfills, because this is preceded by a preferred leaching of soluble substance components. Such water cannot be discharged either directly or after conventional treatment into a receiving waterway or into the sewage treatment plant stage due to its heavy load.

The methods previously used for the treatment of liquid waste do not lead to the desired success in reducing the concentration of pollutants to a level which is no longer considered harmful, with reasonable effort. The known processes such as detoxification, neutralization and oxidation also require an increased outlay on chemicals and in many cases increase the wastewater salt load in an unacceptable manner. The situation is particularly extreme for pollutants such as polychlorinated aromatic hydrocarbons, which cause very considerable environmental pollution even in extremely low concentrations and certain derivatizations and whose removal has not yet been satisfactorily resolved.

It is known to discharge wastewater from industry and commercial economy depending on its origin, for example from the area of surface finishing of metals and plastics, from cleaning and degreasing processes, from chemical and petrochemical processes and the like, by means of special treatment processes, such as precipitation of certain ingredients , Process the conversion of toxic ingredients into non-toxic compounds, cleavage of emulsions etc.

Such wastewater treatment processes usually take place in plants with standing or continuous process control. The precipitation products, precipitates, and separable phases formed in these processes are removed from the waste water by mechanical separation and / or by absorption on suitable absorbents. Due to the complexity and the different composition, process combinations are often used. An overview of the current state of wastewater disposal in the metalworking industry can be found in L.Hartinger, paperback of wastewater treatment for the metalworking industry, Volume 1: Chemistry, Carl Hanser Verlag Munich-Vienna, 1976. In the article "Pretreatment by decanting, detoxification and neutralize, "Waste Management in Research and Practice, pp. 78-96, 5 (1978), R. Meixlsperger summarizes the objectives of the pretreatment of special wastes in such a way that their chemical, physical and toxicological properties are to be changed so that they are subsequently recycled , can be burned or deposited. In principle, this pretreatment amounts to the greatest possible separation of the liquid waste into a water phase and an oil and sludge phase, which is then neutralized. On the other hand, a deliberate additional load or loading of the water phase with pollutant components has not been considered, nor has there been a targeted acidification or alkalization of the wastewater before this separation. In most cases, the previously known methods are only inadequate compromise solutions.

Other wastewater treatment processes are based on the fact that the wastewater from industry and commercial economy, often after pretreatment, e.g. through flocculation and precipitation processes, be sent to a biological sewage treatment plant. This produces sewage sludge in which the most diverse pollutants in the waste water can be enriched, so that the utilization of the sewage sludge, for example as a soil conditioner, is often no longer guaranteed. Nevertheless, biological leachate treatment is given high priority because of its technical controllability and the relatively good cleaning results, cf. R. Stegmann, "Cleaning and raining waste leachate under operating conditions", publications by the Institute for Urban Development, TU Braunschweig, 1979.

All previously known wet chemical and physical processes, but also the biological wastewater treatment processes have the disadvantage that they are only able to treat special ingredients or group-specific ingredients. The total amount of wastewater is usually hardly reduced, but is usually increased considerably by adding chemicals and solutions. The chemical additive also causes the wastewater to have a high salt load, which cannot be broken down when discharged into a municipal wastewater treatment plant, but has a full impact on the receiving water. There are therefore not inconsiderable amounts of sludge that have to be deposited or incinerated. In addition, the wet chemical and biological wastewater treatment processes cannot remove some pollutants or groups of pollutants at all. Ammonium ions and amines cannot be removed from the wastewater by precipitation reactions. However, these compounds are extremely questionable because, for example, they have considerable fish toxicity. Even the complete removal of heavy metals and non-biodegradable organic compounds is not possible with the wastewater treatment processes currently being carried out. This is particularly important if the leachate from landfills not only comes from pure household landfills, but also from household waste plus industrial waste landfills or from hazardous waste landfills.

For the treatment of phenol-containing wastewater, DE-A 25 14 862 proposes first adding alkali metal hydroxide to the wastewater and partially evaporating the mixture under washing action and freeing it of volatile products and then distilling the remaining liquid, the steam being introduced into Alkali hydroxide is washed while mineral salts and water are removed from the distillation residue before the organic materials are burned, if necessary. The steam condensate is preferably treated with activated carbon, and the waste water is preferably neutralized by the addition of alkali. The wastewater to be treated has a more or less known composition regarding the impurities (especially phenol, ammonia).

In FR-A 21 87 707, a similarly composed waste water residue mixture, especially containing phenols and ammonia, is prepared for combustion by adding alkali hydroxide solution to partially evaporate volatile products such as ammonia, and then distilling the residue while being steam the alkali wash around the phenolate to spend as completely as possible in the backlog phase. The remaining product is then incinerated. This process is essentially similar to that of DE-A 25 14 862.

A process in which the "solvent water", which makes up the majority of all wastewater, is so largely separated from the adhering total loads that only small amounts of cargo remain and can be removed or that the pollutant remaining in the treated water is economically justifiable Effort to remove and eliminate would significantly enrich the technology. When removing highly contaminated wastewater, it is necessary to clean and process the wastewater, which fluctuates greatly in its composition and has a different structure, in such a way that the ingredients are completely or largely removed so that the water can be fed to the receiving water or the sewage treatment plant, on the other hand, the separated ingredients are probed in a landfill-capable and transportable form in order to rule out any impairment of humans and animals.

The invention is based on the object of separating the complex composite cargo with organic and / or inorganic constituents from the liquid waste in such a way that at the same time extensive wastewater purification and transfer of the cargo into end products which can be safely deposited is achieved.

The method specified in claim 1 serves to achieve this object, with preferred configurations according to claims 2 to 18. A further subject of the invention is a device according to claim 19 suitable for carrying out these methods, with preferred embodiments according to claims 20 to 27.

According to the invention, the wastewater to be treated, which may have a different composition and load depending on its origin, is first adjusted to an acidic or alkaline range with acid or alkali and preferably also during the separation process at this pH, if necessary by adding acid or Lye kept in the case where the acidity / alkalinity of the waste water changes. Suitable acids are the customary and, if possible, non-volatile acids, such as sulfuric acid; suitable alkalis are the alkali hydroxide solutions, such as sodium and potassium hydroxide, and possibly also alkali carbonates.

The preferred pH value ranges for an acidic distillation are pH 2.5 to 4.5 and particularly preferably pH 3.0 to 3.5; the preferred pH values for the alkaline distillation are values greater than pH 11 and preferably a pH of about 12.0 to 12.5.

The choice of means for pH adjustment depends, among other things. also on the special composition of the wastewater, since an additional factor that controls the solution product of inorganic freight components is introduced via the acid anion (cases of poorly soluble metal sulfates or metal carbonates).

The distillation of water with organic and / or inorganic ingredients generally leads to the fact that the non-volatile substances remain under the distillation conditions in the distillation residue and that various substances, sometimes azeotropic, get into the distillate phase together with the water vapor. However, due to the very complex system, there is also a mutual influence, so that it is also possible to separate or separate substances with low volatility that, under certain conditions, a targeted reduction in the concentration of a certain individual substance in the distillation residue is achieved and a water phase is obtained with a reciprocally enriched concentration of the ingredient or its reaction products.

Distillation at acidic or alkaline pH values modifies the distillation behavior of many pollutants in the wastewater load considerably. Depending on the pH conditions, some substances can be changed so that they become volatile or at least distill over with the water vapor as azeotropic substances.

With an alkaline distillation in the range of about pH 12, ammonium ions can become volatile as ammonia and escape as gases. It is also achieved by alkaline distillation that volatile amines are released and / or that saponification cleaves esters and produces alcohols and the like, which are completely or partially azeotropic. On the other hand, when the invention is carried out by means of process control in an alkaline environment, acids in the form of their alkali or alkaline earth metal salts are retained in the distillation residue. Alkaline adjustment also leads to the cleavage of complex salts such as heavy metal complex salts, in particular copper salt complexes with ammonia or amines.

In an acidic process control, for example at a pH of 3.0, amines and / or ammonium compounds as salts of the added acid become more volatile and thereby accumulate in the distillation residue, while, for example, organic acids such as fatty acids and phenols, but also volatile inorganic acids are released and can transition into the distillate phase.

Other parameters for controlling the distillation, the composition of the distillation products and the distillation yield are the usual distillation parameters, such as temperature and pressure.

If distillation is carried out at normal pressure, the temperature can reach up to approx. 125 ° C, which is related to the complex composition of the waste water. However, distillation under reduced pressure is more favorable, a vacuum of about 120 mbar or less, preferably from 80 to 100 mbar, being advantageous, since then temperatures of at most 100 ° C. or even lower distillation temperatures can be used.

Another parameter is given by setting the distillation time.

The distillation yield, i.e. the proportion of distillate from the wastewater is at least 90% in most wastewater, preferably even 95% in primary distillation. In secondary distillation, the degree of distillation is even higher because of the pre-fractionation. The general rule is that at least 50% of the wastewater is separated by distillation.

According to the invention, considerable influences can be exerted on the type of residues and the constituents contained in the distillate, which is considerably enhanced by the use of a double distillation, that is acidic / alkaline or alkaline / acidic (based on the sequence of the first and second evaporator devices in current flow mode) can be opened and opens up a whole range of modulation of the distillation separation options.

The vapor condensate from the primary evaporation is preferably adjusted to a pH in the range from about 12.0 to 12.5 and aftertreated.

In contrast to the complex starting product, the distillates, which now only contain part of the originally existing organic cargo and essentially no purely inorganic cargo, can now be treated by various post-treatment processes (activated carbon treatment, biodegradation, reverse osmosis, treatment with absorber resins) so that a discharge of the clarified and purified water is possible without disadvantages for the environment. The clear water can be fed to the clarification stage or the receiving water of the same.

The distillation residues, which are at least partially removed from the evaporator circuit, are separated from their liquid phase, with the liquid phase (clear run) being returned to the circulation evaporator, while the separated solids are removed or aftertreated (landfill or incineration). A particularly effective and manageable method of aftertreatment is the melting of the residue, possibly after further drying by means of a vacuum system, the pollutants finally decomposing and being deposited as melt material, possibly deposited in a closed container.

For energy reasons, the separation by distillation should be carried out at subatmospheric pressure. In addition, it is thereby achieved that any gases and vapors that arise can be recorded and treated centrally and do not reach the atmosphere untreated.

Dewatering of the circulated solid fraction is also preferably carried out under vacuum in order to achieve a substantial removal of the adhering water phase and to avoid emission.

In the case of an alkaline process, the distillation residues can then even be treated directly in an alkali melt. Organohalogen compounds in particular are decomposed in an alkaline melt, so that non-toxic reaction products are formed which can be safely disposed of. The melting preparation of the distillation residue has the further advantage that the final destruction of pollutants is already possible on site within the plant, so that when it is carried out in a closed system, the transport of a completely pollutant-free good is guaranteed, which no longer causes hazards as when transporting highly toxic products can.

The distillate phase can, if appropriate, be carried out using suitable absorbents, e.g. Activated carbon are passed, whereby the residual organic loads in the distillate phase are removed.

It is advantageous and therefore preferred to add a defoamer oil to the evaporator stage, in particular the primary evaporation, and, if appropriate, to separate off the product passing through foaming and, preferably, to return it to the evaporator stage.

The exhaust air from the vacuum distillation process can also be used via suitable absorption systems, e.g. with activated carbon, or can be fed to an incinerator if it contains harmful loads.

To substances that are volatile or that are converted into volatile substances by the alkaline or acidic setting of the wastewater from the wastewater before the actual one

To remove distillation, the waste water can preferably be freed of these volatile compounds in a stripping column upstream of the distillation. This is often important because the volatile substances would overload the vacuum system and the gas formation during distillation can lead to foam problems.

The vapors emerging from the stripping column can be post-treated or removed without damage, for example by combustion. For example, formed ammonia washed out and converted into ammonium salts.

According to the invention, the process control is chosen so that the waste water is concentrated in the first evaporator stage, the evaporation vapors being used to heat the downstream second evaporator.
As already mentioned, it is advantageous to start the distillation first in acid or alkaline and to distill the distillates resulting from this distillation again while adjusting the pH in the opposite direction.

For the aftertreatment of the distillate, it may be advantageous to adjust the pH to a neutral pH, preferably about 6 to 8. In this form it can, for example, be treated well with activated carbon.

In particular, the treatment of waste water with proportions of polyhalogenated mono- or polynuclear aromatic and / or other cyclic compounds leads to a separation of these substances into the three possible fractions (distillation residue, distillate, waste air), from which they are then either removed or together with the residues separated from the water can be deposited, burned or removed by melt. The method according to the invention Thus, especially with regard to the highly polluting and non-biodegradable pollutants, enables a way to fall below certain maximum concentrations or to undercut the minimum requirements of the limits by far.

The invention finds particular application in waste water which contains polychlorinated compounds such as hexachlorocyclohexane, polychlorinated biphenyls, polychlorinated dibenzofurans, polychlorinated dibenzodioxins or chlorophenol derivatives.

• 1) der vom Volumen her stark verminderte Destillationsrückstand in eine feste Phase überführt wird, deren Handhabung (Abfüllung in Gebinde; Transport und dergl.) wesentlich erleichtert wird und die in dieser Form sowohl in geeigneten Deponien abgelagert, in dafür zugelassenen Verbrennungsanlagen verbrannt oder aber durch alkalische Schmelze - diese Nachbehandlung wird bevorzugt - unter Zersetzung der Organohalogenverbindungen entgiftet werden kann;
• 2) die Destillate befreit sind von der Hauptmenge der Fracht und somit keine festen Schmutzstoffe und nichtverdampfbare Verbindungen mehr enthalten. Lediglich leichtflüchtige und wasserdampf-flüchtige organische Substanzen verbleiben im Destillat und je nach pH-Werteinstellung in anderem Verhältnisanteil, auf jeden Fall meistens jedoch in einer gegenüber der Menge in der Ausgangsfracht stark verringerten Menge; aus dem Destillat können sie durch gezielte Nachbehandlung, wie z.B. durch Aktivkohlebehandlung, entfernt werden (die Behandlung des eingesetzten Abwassers direkt mit Aktivkohle ist in der Regel bei komplex zusammengesetzten, verschmutzten Abwässern wirtschaftlich und technisch nicht durchführbar);
• 3) eventuell entstehende Abgase aus der Vakuumanlage oder hinter der Strippkolonne ebenfalls so behandelt werden können, daß sie wiederverwertet, verbrannt oder an einem geeigneten Absorptionsmittel abgeschieden werden.

The invention ensures that problematic wastewater can be broken down into three fractions by a simple thermal separation process in a closed apparatus or system, the loads of the wastewater being separated and distributed in these fractions in such a way that

• 1) the distillation residue, which is greatly reduced in volume, is transferred to a solid phase, the handling of which (filling in containers; transport and the like) is made considerably easier, and which in this form is either deposited in suitable landfills, burned in approved incineration plants or by alkaline melt - this aftertreatment is preferred - can be detoxified by decomposing the organohalogen compounds;
• 2) The distillates are freed from the bulk of the cargo and therefore no longer contain solid contaminants and non-evaporable compounds. Only volatile and steam-volatile organic substances remain in the distillate and, depending on the pH setting, in a different proportion, but in any case mostly in a quantity that is greatly reduced compared to the quantity in the original freight; They can be removed from the distillate by targeted post-treatment, such as by activated carbon treatment (the treatment of the waste water used directly with activated carbon is generally not economically and technically feasible in the case of complexly composed, contaminated waste water);
• 3) Any exhaust gases that may arise from the vacuum system or behind the stripping column can also be treated in such a way that they are recycled, burned or at one suitable absorbent can be separated.

The invention has proven particularly useful in the case of highly contaminated wastewater containing polyhalogenated aromatics. In contrast, the treatment of wastewater with proportions of polychlorinated compounds leads to the disadvantage in conventional wet chemical and biological wastewater treatment or in a combination of such processes that the qrganohalogen compounds then in large amounts of water-containing sludge, in the absorbents or in the sewage sludge in low concentration, but mostly in high volumes, are enriched, which can only be disposed of by depositing them in special landfills or by incinerating hazardous waste.

The invention also proposes a device for carrying out the new method, with a device 1 for pH adjustment; a first evaporator device 7, consisting of one or more evaporator stages with a circulation system, which contain a steam separator 8, a heat exchanger 9 and a pump 10 for circulating the waste water to be evaporated; a condenser 14 for condensing the vapors from the primary evaporation; a device for aftertreatment of the evaporator vapor condensate; a device 16 for solids separation, in which the distillation residue is separated into solids and clear run; and a device 17 for returning the clear run to the corresponding stage of the evaporator device 7.

The evaporator device 7 is preferably connected to a vacuum system 27.

The device for the aftertreatment of the vapor condensate preferably contains a collecting container 46 for the vapor condensates of the individual stages of the evaporator device, optionally means 47 for adjusting the pH value and an activated carbon filter 48 as well as advantageously a device 28 for adjusting the pH value of the condensate and a second evaporator device 29 with at least one Evaporator stage, consisting of a steam separator 30, a heat exchanger 31 and a circulation system 32, this second evaporator device 29 being connected to the heat exchanger 9 of the first evaporator device 7 via a line 33 which conducts the evaporation vapors into the heat exchanger, and a device 34 for Post-treatment of the condensate from this second evaporator device 29 is provided.

It is preferably located between the device 1 for pH adjustment and the evaporator device 7 a stripping device 36, with a stripping column 36a, a steam supply line 37, a stripper steam extraction 38 and a transport line 39 for stripped waste water for transfer into the evaporator device 7.

The device for aftertreatment of the vapor condensate preferably contains means 34 for pH adjustment and an activated carbon filter 40.

A preferred embodiment of the device is characterized in that the device 16 for solids separation is connected to a vacuum dewatering device 41 and a line 42 is provided for returning the dewatering filtrate to the corresponding stage of the evaporator device 7. It is particularly expedient to connect the device 16 for solids separation to a melting device 43 which contains means 44 for melting the solids and means 45 for supplying melting aids such as alkali salts.

The individual evaporator stages of the evaporator devices 7 and 29 are preferably equipped with droplet separators 11 and 35, respectively, which are coupled to a measuring device 11a or 35a in such a way that, in the event of overflowing, a signal is generated by the drain formed on the droplet separator, which indicates the automatic feed of defoamer oil triggers via line 13 to the evaporator stage.

Preferred embodiments of the invention are explained below with reference to the accompanying drawings, Figures 1 to 5.

• Fig. 5 ein allgemeines Prinzipschema des Verfahrens gemäß der Erfindung, wobei in diesem Schema alle wichtigen Kombinationsmöglichkeiten, wie sie auch Gegenstand der die bevorzugten Ausführungsformen betreffenden Unteransprüche sind, dargestellt sind. Selbstverständlich sind auch andere, nicht dargestellte Ausgestaltungen möglich, soweit sie unter den Schutzbereich der Ansprüche fallen.
• Fig. 1 ist ein Fließbild einer Ausführungsform des Verfahrens gemäß der Erfindung, mit zunächst saurer Primär-Eindampfung des Abwassers und anschließend alkalischer Sekundär-Eindampfung des in der Primär-Eindampfung erhaltenen Destillats. Die Bezeichnungen "Primär"-Eindampfung bzw. "Sekundär-Eindampfung" stehen synonym für die erste und weitere Verdampfungseinrichtung.
• Fig. 2 ist ein Fließbild einer bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens, mit alkalischer Monodestillation und vorgeschalteter Strippung.
• Fig. 3 ist ein Fließbild einer bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens mit alkalischer Monodestillation nach vorgeschalteter Strippung, welche insbesondere bei Abwässern mit Gehalten an polycyclischen aromatischen und anderen cyclischen organischen Verbindungen angewendet wird.
• Fig. 4 ist ein Fließbild einer Ausführungsform des erfindungsgemäßen Verfahrens mit saurer Monodestillation, wobei in diesem Fall als Beispiel eine zweistufige Eindampfung als eine der möglichen Varianten zwischen ein- und x-stufiger Eindampfung dargestellt ist. Auch diese Ausführungsform wird speziell bei Abwässern mit Gehalten an polycyclischen aromatischen und anderen cyclischen organischen Verbindungen angewendet.

In detail shows

• 5 shows a general schematic diagram of the method according to the invention, all important possible combinations, as are also the subject of the subclaims relating to the preferred embodiments, being shown in this diagram. Of course, other configurations, not shown, are also possible, provided that they come within the scope of the claims.
• Fig. 1 is a flow diagram of an embodiment of the method according to the invention, with first acidic primary evaporation of the waste water and then alkaline secondary evaporation of the distillate obtained in the primary evaporation. The terms "primary" evaporation or "secondary evaporation" are synonymous with the first and further evaporation devices.
• Figure 2 is a flow diagram of a preferred embodiment of the process of the invention, with alkaline monodistillation and upstream stripping.
• FIG. 3 is a flow diagram of a preferred embodiment of the process according to the invention with alkaline monodistillation after upstream stripping, which is used in particular for waste water with contents of polycyclic aromatic and other cyclic organic compounds.
• FIG. 4 is a flow diagram of an embodiment of the process according to the invention with acidic monodistillation, in which case, as an example, a two-stage evaporation as one of the possible variants between one-stage and x-stage Evaporation is shown. This embodiment is also used specifically for wastewater containing polycyclic aromatic and other cyclic organic compounds.

In the embodiment of the method according to the invention shown in FIG. 1, the waste water is fed via the waste water feed line 102 to a device for adjusting the pH value 101, in which the pH value is adjusted to one by adding acid (104) using a mixing element 105 acidic range and is preferably lowered to about 3-4. With the aid of the waste water pump 103, the pretreated waste water is fed to the evaporator device 107. The evaporator device 107 essentially consists of the steam separator 108, the heat exchanger 109 and the circulation pump 110. The vapor from the secondary evaporator device 129, which is fed to the heat exchanger 109 via the line 133, heats up and partially evaporates the waste water with a simultaneous increase in the concentration the saturation limit, based on at least one of the ingredients. The evaporation vapors are fed to the surface condenser 114 via the droplet separator 111 and condensed here. Droplets separated in the droplet separator 111 are fed back to the evaporator device 107 via the return line 112. If the amount increases sharply, e.g. when the steam separator is foamed, a signal is automatically triggered by a measuring probe 111a and, as a result, defoamers are metered in via line 113 to destroy the foam. A partial stream of the circulating liquid containing supersaturated and partially crystallized solids is fed continuously to a solids separator 116, from which the filtrate returns to the evaporator device via line 117 after the solids have been discharged. The discharged solids are stored in suitable containers at the landfill or transferred to landfill-ready end products in some other way, aftertreatment being provided if necessary.

The gases that are not condensable in the surface condenser 114 are sucked off by a vacuum pump 127 and, if necessary, fed to a cleaning stage or to the combustion. The distillate from the surface condenser 114 flows into a container for adjusting the pH 128, in which the pH is raised to an alkaline range, preferably to approximately 12-12.5, by adding alkali. With this alkaline pH value (preferably at pH 12-12.5), the primary distillate flows into the secondary evaporation device 129, which in turn consists of a steam separator 130 with a heating element 131 and a circulation line 132. A circulation pump analog 110 is not used in many cases due to the relatively high purity of the distillate. The vapors are also passed through a droplet separator 135 and fed through the connecting line 133 to the radiator 109 of the primary evaporator device, where they condense while releasing their heat of vaporization. The distillate II thus obtained flows into a further container 134 for pH adjustment, in which the pH value is reduced, for example, to a value of 6.5 to 8 by adding acid. From here, the distillate can be fed to the receiving water or reused as process water, whereby depending on the quality requirements, a cleaning stage, e.g. A carbon filter can be installed downstream. The latter is necessary in the case of waste water which contains impurities with toxic compounds, in particular the polyhalogenated aromatic cyclic compounds.

In the preferred embodiment of the method according to the invention shown in FIG. 2, the wastewater is fed via the wastewater feed line 202 to a container for adjusting the pH value 201, in which the pH is adjusted to an alkaline by adding lye via 204, using a mixing element 205 Range, preferably a pH range of about 12 to 12.5, is raised. With the aid of the wastewater pump 203, the pretreated wastewater is fed to the stripping column 236a, in which the steam is added via 237 volatile components, such as ammonia in particular, are driven off. Via the connecting line 238, the expelled steam together with the exhaust air 206 from the container for pH adjustment is fed to a combustion or aftertreatment. It is possible, depending on the proportion of NH₃ to connect a targeted further processing. The stripped waste water reaches the evaporator device 207 via the connecting line 239, which consists of the steam separator 208, the heat exchanger 209 and the circulation pump 210. The evaporation vapors generated by indirect heating are fed to the surface condenser 214 via the droplet separator 211 and condensed here. Droplets separated in the droplet separator 211 are fed back to the evaporator device 207 via the return line 212. If the amount rises sharply, for example when the steam separator 208 is being foamed, a signal is triggered by the measuring probe 211a and, as a result, defoamers are automatically metered in via line 213 to destroy the foam. A partial flow of the supersaturated and possibly crystallized circulating liquid containing solids is fed continuously to the solids separator 216, from which the filtrate is returned to the evaporator device 207 via line 217 after the solids have been discharged. The discharged solids are stored in suitable containers at the landfill and / or post-treated and transferred to a landfill material. The gases which are not condensed in the surface condenser 214 are sucked off by a vacuum pump 227 and, if appropriate, fed to a cleaning stage or combustion. The distillate from the surface condenser 214 flows into a container for pH adjustment 228, in which the pH is lowered to a neutral range, preferably to about 6.5 to 8, by adding acid. From here, the distillate can be fed to the receiving water or reused as process water, whereby depending on the quality requirements, a cleaning stage, for example with an activated carbon filter, can be added if necessary.

In the preferred embodiment of the method according to the invention shown in FIG. 3, the wastewater contaminated with polychlorinated constituents is fed via a feed line 302 to a container for pH adjustment, in which the pH is raised by adding lye 304 using a mixing element 305 to an alkaline range, preferably about 12 to 12.5. With the aid of the wastewater pump 303, the pretreated wastewater is fed to the stripping column 336a, in which the volatile constituents entrained by adding steam are expelled via line 337. These are fed via line 338 together with the exhaust air from the container for pH adjustment via line 306 to a combustion or aftertreatment or both. The stripped wastewater then passes via the connecting line 339 into the evaporator device 307, which consists of the steam separator 308, the heat exchanger 309 and the circulation pump 310. The evaporation vapors generated by indirect heating are passed over the droplet separator 311 and fed to the surface condenser 314, in which the condensation takes place. Droplets separated in the droplet separator 311 are fed back to the evaporator device 307 via the return line 312. If the return quantity rises sharply, for example as a result of the steam separator 308 being foamed, a signal is triggered by the measuring probe 311a and, as a result, defoamers are automatically metered in via line 313 to destroy the foam. A partial stream of the supersaturated and mostly solids-containing circulating liquid is continuously fed from the evaporator device 307 to the solids separator 316, from which the filtrate returns to the evaporator device via line 317 after the solids have been discharged.
The discharged solid is either sent to a special waste incinerator or underground storage, but preferably transferred to a melt in suitable autoclaves, the pollutants contained, such as polychlorinated compounds, decomposing as a result of the alkaline environment.

The gases which are not condensed in the surface condenser 314 are sucked off by a vacuum pump 327 and, together with the stripper exhaust steam 338 and the exhaust air from the container for pH adjustment 306, are fed to an activated carbon filter or an incinerator. The distillate from the surface condenser 214 flows into a pH adjustment container 328, in which the pH is lowered to a neutral range, preferably to about 6.5 to 8.0, by adding acid (347). Traces of pollutants that may still be present in the distillate are removed in a downstream activated carbon filter 348 before the purified distillate leaves the system. The used activated carbon from the exhaust air and the distillate cleaning can preferably be burned without problems in a special waste incinerator or stored in a landfill or treated chemically and physically.

In the embodiment of the method according to the invention shown in FIG. 4, the wastewater contaminated with polychlorinated ingredients is fed via the feed line 402 to the container for pH adjustment 401, in which the pH is added by adding acid via 404 using a mixing element 405 is lowered to an acidic range, preferably to about 3 to 4. With the help of the waste water pump 403, the pretreated waste water is fed to the preconcentration stage 418. The pre-concentration stage 418 consists of the steam separator 419, the heat exchanger 420 and the circulation pump 421. Indirect heating via the heat exchanger 420 causes part of the water contained in the waste water to be evaporated and the evaporation vapors formed are transferred to the heat exchanger 409 via the droplet separator 422 and the line 424 the downstream evaporator stage 407 supplied. A measuring probe 411a is again installed in the return line 423 from the droplet separator 422 to the preconcentration stage 418. which triggers a signal in the event of excessive liquid outflow, as is caused when the steam separator 419 is foamed, by which defoamer is automatically metered in via line 413 to destroy the foam.

From the preconcentration stage 418, the preconcentrated wastewater reaches the evaporator stage 407 via line 425, which, like the first stage, consists of steam separator 408, heat exchanger 409 and circulation pump 410. The heat supplied with the vapors from the pre-concentration stage 418 further evaporates the waste water in this stage beyond the saturation limit of at least one or more ingredients or a group of ingredients, so that solids can crystallize out. The evaporation vapors are fed to the surface condenser 414 via the droplet separator 411 and condensed there. With the aid of the measuring probe 411a arranged in the return line 412 from the droplet separator to the evaporator stage, an automatic foam destruction is effected if necessary analogously to stage I. A partial stream is continuously withdrawn from the circulating liquid of the evaporator stage 407 and fed to the solids separator 416, through which the solids are discharged. The filtrate returns to the evaporator stage via line 417. The separated solid is either broken down into an underground landfill, incineration of special waste or, preferably, after the addition of alkali salts to establish an alkaline environment in an alkaline melt.

The uncondensed gases from the surface condenser and from the vapor-heated heat exchanger 409 of the second stage are extracted with the aid of vacuum pump 427 and, together with the exhaust air 406 from the container for pH adjustment 401, are fed to an activated carbon filter or an incinerator. In the container for pH adjustment 446, the vapor condensates from the heat exchanger 409 and from the Surface capacitor 414 is adjusted to a pH in the neutral range, preferably to a pH of about 6.5 to 8.0, by adding alkali. The vapor condensate is then cleaned in an activated carbon filter 448 before it leaves the system.

The two-stage embodiment described in the example shown in FIG. 4 can correspondingly also be used for the embodiments described in FIGS. 1 to 3 or can also be supplemented with further stages if this makes sense for heat-economic reasons.

1 to 4 parts of the same function, which do not necessarily have to be of identical construction, are identified by matching final digits less than 100. For example, 107 denotes the evaporator device of FIGS. 1 and 307 the evaporator device of FIG. 3.
The following list of reference symbols explains the individual parts of the device. This list is part of the present description.

Claims (27)

1. A process of separating the complexly composed load made up of organic and inorganic component materials from liquid wastes containing dissolved solids, such as industrial waste waters and sanitary landfill leachates, by distillation treatment, characterized
      by adjusting the waste water pH level to an acid or alkali range and then separating the waste water by distillation in a primary evaporator stage into evaporation vapours and a distillation residue such that
      at least a portion of said volatile load is distilled off together with the vapours and
      the distillation residue is supersaturated with respect to at least one of said component materials;
      by condensing and post-treating the evaporation vapours in a condenser so as to separate the dragged-along load to the point where the water phase may be passed on to a drainage canal or to a clarification system; and by optionally adjusting the primary evaporation condensate to another pH range prior to post-treatment and passing it on to a secondary evaporator;
      by withdrawing at least part of the supersaturated distillation residue from the evaporator stage and subjecting it to a solids separation treatment; and
      by returning the liquid cleared of the solids to the primary evaporator stage.
2. A process as in claim 1, characterized in that the liquid wastes to be treated are hazardous wastes or parts thereof which contain amounts of polychlorinated mono- or polycyclic aromatic and/or other cyclic compounds.
3. A process as in claim 1 or 2, characterized in that the liquid wastes contain organic compounds from the group comprising hexachlorocyclohexanes, polychlorinated biphenyls, polychlorinated dibenzofurans, polychlorinated dibenzodioxines and/or chlorophenol derivatives.
4. A process as in any one of claims 1 to 3, characterized by performing the distillative separation under application of subatmospheric pressure, preferably of less than approx. 120 mbar.
5. A process as in any one of claims 1 to 4, characterized by maintaining the waste to be separated by distillation at a pH level in the range of approx. 3.0 to 3.5.
6. A process as in any one of claims 1 to 4, characterized by maintaining the waste to be separated by distillation at a pH level in the range of approx. 12.0 to 12.5.
7. A process as in any one of claims 1 to 6, characterized by passing the vapour condensate over an active coal filter and clearing it at leastly partly of its organic load.
8. A process as in any one of claims 1 to 7, characterized by adjusting the pH level of the vapour condensate to a range of approx. 6 to 8 prior to the post-treatment thereof.
9. A process as in any one of claims 1 to 8, characterized by adjusting the pH level of the primary evaporation vapour condensate to a range of approx. 12.0 to 12.5 and post-treating it.
10. A process as in any one of claims 1 to 9, characterized by performing the primary and secondary evaporations one after the other in respect to thermal flow.
11. A process as in any one of claims 1 to 10, characterized by adjusting the pH level of the secondary evaporation condensate to approx. 6 to 8 and post-treating it.
12. A process as in any one of claims 1 to 11, characterized by metering an antifoaming oil into the evaporator stage, particularly the primary evaporator stage, and by optionally separating and preferably returning to the evaporator stage the product going over by overfoaming.
13. A process as in any one of claims 1 to 12, characterized by alkali stripping the waste water in a stripper column prior to its entry in the evaporator stage.
14. A process as in claim 13, characterized by post-treating the vapours discharged at the head of the stripper column.
15. A process as in any one of claims 1 to 14, characterized by pre-concentrating the waste water fed to the evaporator stage in at least one pre-concentrating stage and by using the vapours obtained in the pre-concentrating stage for heating the subsequent stage.
16. A process as in any one of claims 1 to 15, characterized by further dehydrating the separated solid material, preferably in vacuum, and by returning the dehydration filtrate to the evaporator stage.
17. A process as in any one of claims 1 to 16, characterized by melting the separated solid material together with alkali salts, decomposing it and thus converting it into a disposable and transportable final product.
18. A process as in any one of claims 4 to 17, characterized by post-treating the air exhausted from the vacuum equipment in the distillative separation at subatmospheric pressure.
19. Apparatus for practicing the process of claim 1, comprising
       pH adjusting means (1);
       evaporator means,
       comprising a primary evaporator stage (7) and one or several optional secondary evaporator stages, each with a recycling system containing a steam separator, a heat exchanger and a pump for recirculating the waste to be evaporated;
       condensing means (14) for condensing the primary evaporation vapours;
       means for post-treating the evaporator vapour condensate;
       solids separation means (16) for separating the distillation residue into solids and cleared liquid; and
       means (17) for returning the cleared liquid to primary evaporator (7).
20. Apparatus as in claim 19, characterized by evaporator means (7) being connected to a vacuum system (27).
21. Apparatus as in claim 19 or 20, characterized by the vapour condensate post-treating means comprising a container (46) for collecting the vapour condensates from the individual stages of the evaporator means, optional pH adjusting means (47), and an active coal filter (48).
22. Apparatus as in any one of claims 19 to 21, characterized by the vapour condensate post-treating means including means (28) for adjusting the pH level of the condensate and by second evaporator means (29) comprising at least one evaporator stage, consisting of a vapour separator (30), a heat exchanger (31) and a recirculating system (32), said second evaporator means (29) being connected to heat exchanger (9) of first evaporator means (7) through a line (33) for conducting the evaporator vapours into the heat exchanger, and means (34) for post-treating the condensate from said second evaporator means (29).
23. Apparatus as in any one of claims 19 to 22, characterized by stripping means (36) disposed between pH adjusting means (1) and evaporator means (7), said stripping means comprising a stripping column (36a), vapour feedline (37), and stripper vapour discharge (38) and a transport line (39) for conducting stripped waste water to evaporator means (7).
24. Apparatus as in any one of claims 19 to 23, characterized by said vapour condensate post-treating means comprising pH adjusting means (34) and an active coal filter (40).
25. Apparatus as in any one of claims 19 to 24, characterized by solid separating means (16) being connected to vacuum dehydrating means (41), and by a line (42) being provided for returning the dehydration filtrate to primary evaporator (7).
26. Apparatus as in any one of claims 20 to 26, characterized by solids separating means (16) being connected with melting means (43) comprising means (44) for melting said solids and means (45) for feeding in melt-promoting materials such as alkali salts.
27. Apparatus as in any one of claims 19 to 27, characterized by the individual evaporator stages of evaporating means (7, 29) being equipped with drop separators (11, 35) coupled to measuring means (11a, 35a) in such a manner that the discharge formed at the drop separator in the case of overfoaming causes a signal to be generated which triggers the automatic feeding of antifoaming oil to the evaporator stage through a line (13).

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